0331 - Biostatistics I - Sampling - VY Flashcards Preview

What is the difference between probability sampling and non-probability sampling

Probability = determinable change of an individual being sample.Non-probability= non-determinable chance of an individual being sampled.Probability sampling is where the sample is chosen in a way which allows you to determine how likely an individual is to be sampled. Non probability sampling is where the sample is chosen in a way that makes it impossible to determine how likely it is that an individual from the population is included in the samle.

2

List some descriptions of the central tendency

Mean – the average. Median – the middle point of data where 50% of data points lie above and belowMode - number with the highest frequency

3

List some measures of data variability

Range, Variance, Standard deviation and Standard error

4

What is systematic sampling? give an example of systematic sampling

Systematic sampling = sampling from a list where every x individual is chosen (x = any number). E.g. picking every 3rd student in the medical cohort list

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What is simple random sampling? Give an example of simple random sampling

Simple random sampling = everyone in population has equal chance of being sample. E.g. putting all the names of ANU students in a hat and randomly drawing

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What is stratified sampling ? Give an example of stratified sampling

Stratified sampling = population is divided in strata (subgroups) and random sample is taken from each. E.g. dividing medical cohort into guys and girls and sampling 15 of each

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What is cluster sampling? Give an example of cluster sampling

Cluster sampling = cluster (groups) are selected from population and random samples are taken from selected clusters. E.g. surveying residents of Canberra by sampling selected streets in key suburbs

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What is convenience sampling? Give an example of convenience sampling

Convenience sampling = using any people that are available for research. E.g. asking medical students who are in front of peter baulme building to do a survey

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What is quota sampling?Give an example of quota sampling

Quota sampling = sampling to fill a predetermine quota. E.g. recruiting medical students for a survey until a quota from each academic background is filled

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What is purposive sampling? Give an example of purposive sampling

Purposive sampling = selecting individuals based on knowledge of a population, purpose of study and some characteristic of selectees.E.g. Selecting individuals that exemplify a 'typical med student'

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What is snowball sampling? Give an example of snowball sampling

Snowball sampling = existing study subjects recruit other subjects from among their acquaintance..E.g. selecting a few 'typical med students' who then ask their friends/colleagues to participate

List some types of probability sampling and non-probability sampling

What is nominal data? Is it a discrete or continuous category of data? Give an example

Nominal data = assigning a code to a value or characteristic (number has measurable value). It is a discrete category. E.g. Assigning males = 1 and females = 2

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What is ordinal data? Is it a discrete or continuous category of data? Give an example

Ordinal data = assigning a ranked code to a value or characteristic (number has measurable value). It is a discrete category. E.g. how do you feel : 1=good, 2=ok, 3=not great, 4=terrible

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What is interval scale? Is it a discrete or continuous category of data? Give an example

Interval scale= scale where distance between adjacent intervals is the same but the zero point is arbitary (does not exist). It is a continuous category. E.g. Measuring temperature (0 degrees does not mean no temperature)

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What is Ratio scale? Is it a discrete or continuous category of data? Give an example

Ratio scale = values / observations may take on any value and the zero is a true zero (i.e. it exists). It is a continuous category. E.g. height (0cm = no height)

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What is the range of a data set

Range – the difference in between the highest and lowest value

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What is the variance of a data set

Variance – a measure of how far a set of numbers is spread out. Small variance indicates the data points are very close to the mean and vice versa for a large variance

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What is the standard deviation of a data set

Standard deviation – the square root of variance. It is also a measure of how much variation there is in a dataset from the mean. Unlike variance, it is expressed in the same units as the data

20

What is the standard error of a data set

Standard Error - a measure of the statistical accuracy of an estimate. It is the standard deviation of the sampling distribution of the sampling mean